Questions tagged [crystal-structure]

In mineralogy and crystallography, a crystal structure is a unique arrangement of atoms or molecules in a crystalline liquid or solid.

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1answer
108 views

How can the bulky octadecyltriethoxysilane molecule promote single-crystal growth?

Octadecyltriethoxysilane is very bulky (source), yet it was used to promote single crystal growth (source). How can such a bulky molecule induce crystal growth? (For example epitaxial growth happens ...
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269 views

What are the bubbles and crystals found in sodium acetate hot packs after use and storage in the solid form?

When sodium acetate trihydrate hot packs are regenerated soon after activation, they regenerate to a clear liquid upon boiling (typically with an air bubble that was not present in the new pack) On ...
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92 views

Drying the solution of two salts

What will be the arrangement of crystals if a solution of two salts, say, Sodium Chloride and Potassium Chromate, is dried? Will one salt crystallize before the other and become the crystallization ...
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167 views

Would a melted crystal recrystallize back into the same lattice structure when frozen?

Two things that I'm not sure about melted crystals: For a material that has only one possible crystal structure, would freezing cause it to recrystallize, or could it become amorphous upon freezing? ...
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Growing crystals that are in a magnetic field or subjected to an electric field

I know different crystals resonant at different frequencies but is it possible to grow crystal at a certain frequency. An example would be growing crystals using Epsom salt or Alum in a magnetic ...
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Hexagonal unit cell vs crystal system

Is the hexagonal unit cell (resulting from hexagonal closed packing) same as the unit cell of hexagonal crystal system? The unit cell of hexagonal crystal system is described by the following sides ...
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How does VB theory explain the bond angles in SiO2?

Silicon dioxide has a huge variety of structures. Most of them have a tetrahedral $\ce{SiO2}$ unit cell — the $\ce{O–Si–O}$ angle is $109.5°$, accordingly. The VB/hybridization approach to this ...
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730 views

What is the difference between crystal structures of proteins, organic and inorganic materials?

From the definition of crystal and the main differences between crystalline and amorphous material, it is known that crystal formation requires ordered bonding between atoms or molecules. How can ...
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Aren't unit cell and the relevant crystal similar?

"A crystal is formed by a large number of repetitions of basic pattern of particles in space. The basic structural unit which when repeated in three spatial directions generates the crystal ...
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386 views

Is NaCl crystal always going to have even number of atoms?

I just read: In $\ce{NaCl}$, atoms don't aggregate so as to form discrete molecules but they are held together in a network structure. The ratio of the $\ce{Na}$ to $\ce{Cl}$ atoms in a sodium ...
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87 views

Lattice structures, Metallic Bonding

How and under what circumstances can cations form a lattice structure? Would they not repel each other?
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Why is a face-centred cubic unit cell not regarded as equivalent to a body-centred tetragonal unit cell? [duplicate]

When studying crystal lattices, I decided to learn which combinations of unit cells and lattice systems lead to the 14 Bravais lattices. I learnt that, for example, no centred triclinic unit cell ...
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General notation for one of the d-orbitals

What is the general notation to represent the d-orbital with $l=2$, $m_l=0$, i.e. the orbital normally referred to as $\mathrm{d}_{z^2}$. To elaborate more, this orbital can be ordered in various ways ...
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Replicating an illustration for the crystal structure of ferrihydrite

I came across this image of crystal structure in an article The Structure of Ferrihydrite, a Nanocrystalline Material [1]: Does someone know the software in which it was produced? I have been looking ...
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1answer
114 views

Are adamantane crystals covalently bonded?

I'm writing a report and need one thing clarified after reading the Wikipedia article on adamantane: 'All the above methods yield adamantane in the form of polycrystalline powder. Using this powder, ...
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1answer
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Why some compounds form different crystal structure at different temperature?

Lets take an example :- Sodium superoxide has three different crystal structure, the marcasite structure at nearby 81 K, the pyrite structure between 196 K and 223 K and calcium carbide ...
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1answer
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Solid state, closed packed structures, BCC lattice [closed]

How many next nearest neighborhood respectively each potassium has in bcc lattice?
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Is there any porous material that can have narrow parallel and “perfectly straight” cavities/holes through it (or bored through it)?

I'm basically looking for a material that can allow photons to pass through its cavities, but only those photons that travel at an angle (almost) exactly perpendicular to the materials surface. Non-...
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Chemical bond at Aluminum / Aluminum oxide interface

I am trying to find out what chemical bond holds aluminum oxide to the aluminum on which it forms. The only information I was able to find on the internet was in a Google book which suggested that the ...
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1answer
80 views

Why is quickly cooling a a hot pan bad for it?

I've heard that really quickly cooling a hot pan is bad and reduces the lifetime of the pan. I'm wondering, from a chemical perspective, why this would be true. My thought is that as a pan is heated ...
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Structure of KC8

Graphite reacts with potassium to produce a compound with the empirical formula $\ce{KC8}$. Of the following, which is the best description of this compound's structure? (a) $\ce{K+}$ ions close ...
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1answer
567 views

Why does ice freeze the way it does?

I was just recently looking into some of the details of the different crystal structures that ice can freeze in. I was aware that many of the unusual properties of ice $I_h$ (the structure of “...
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2answers
461 views

Freezing all the water on earth with a seed crystal

I was recently reading the satirical, fictional book Cat's Cradle by Kurt Vonnegut. In this book, one of the major subplots is the invention of a mythical polymorph of ice called ice-9 in the book. In ...
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Why does phosphorus give a free electron in silicon doping?

Extrinsic semiconductors are created by doping an intrinsic semiconductor; typically silicon is doped with phosphorus to create free electrons or boron to create "holes". In the case of phosphorus ...
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781 views

Why is Cubic closed packing called “cubic”?

How is Cubic Closed Packing "cubic" and also how is hexagonal closed packing "hexagonal" ? I have been thinking over this since a few hours but I am unable to visualise. I understand that when ...
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Why are there only 7 types of unit cells and 14 types of Bravais lattices?

Why are there only 7 types of unit cells and 14 types of Bravais lattices? I was reading about solid-state chemistry for the first time and this limitation made no sense to me. I tried to do the ...
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1answer
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How do we identify left handed and right handed crystals?

I was going through this article about how Louis Pasteur studied and explained the absence of optical activity in Racemic acid. Here's an extract: When Pasteur next examined crystals of the same ...
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Fermi Level of an alloy

How could one calculate the Fermi level of a copper-nickel alloy? They are both structurally face-centered cubic, however how would this structure affect the Fermi level of the individual atom or the ...
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How would I find an apporpriate dopant element for a lattice

I am trying to figure how would I go about finding a dopant element that would fit in a copper lattice? I already have the data for the atomic dimensions and structure (available below), however how ...
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Why do we not see silicon in a structure like graphite?

Silicon exists in a structure similar to diamond, with 4 silicon atoms bonded to each other in a tetrahedron. Why do we not see it exist in a structure like graphite? Is it even possible to get ...
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1answer
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Why does the dielectric constant of a solid increase due to a Frenkel defect?

In crystalline solids, an atom may be displaced from its original position in order to create a vacancy in the original location. This is referred to as a Frenkel defect. Why does this defect result ...
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1answer
2k views

Calculating Molar Volume from crystal volume

I am trying to calculate molar volume of certain crystal lattices to be used for crystal growth kinetics calculations. The information I have is the crystal volume & crystal lattices. For example ...
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Why is SiO2 a solid while CO2 is a gas?

I was under the impression that chemistry almost exclusively involves valence electrons because there isn't enough energy to strip off electrons located closer to the nucleus. If that is true, and ...
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2answers
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What bond\crystal has the most regular pattern (i.e. least irregularities)? [closed]

Salt is a famous regularly repeating cubic crystal, but there are always natural deformities and flaws present. I have heard that graphene is an extremely uniform substance. With these in mind, what ...
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282 views

Data repository of organic compounds

Does there exist any data repository of chemical compound that gives the structure of the compounds with the help of coordinate geometry. It would be like each atom has a coordinate and the list of ...
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3k views

Why does sodium polyacrylate solidify, on addition of water?

Sodium polyacrylate is a white powder with a characteristic odor. But when we add water to this powder, instead of forming an aqueous solution, it instantaneously solidifies and forms more amount of ...
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4answers
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Number of atoms in NaCl unit cell

Consider this picture of an $\ce{NaCl}$ unit cell: It appears to show 14 $\ce{Cl-}$ ions and only 13 $\ce{Na+}$ ions. Given that discrepancy, how is table salt balanced for charge? Why isn't there ...
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1answer
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Extracting “Crystal Radii” from a CIF file

I'm currently downloading .cif files from various online databases and using openbabel to convert the fractional coordinates that are in the .cif files into .xyz files. The typical output will look ...
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1answer
724 views

What are the structures of potassium superoxide and xenon hexafluoride? [closed]

I have 2 questions in mind: 1) What is the structure of the superoxides? More specifically, what is the structure of $\ce{KO_2}$? 2) What is the structure of and dipole moment for $\ce{XeF_6}$?
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1answer
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Why can oxygen have a coordination number of 3 in a complex between silver and SiO2?

I am running an MD simulation of silver with $\ce{SiO2}$. Initially, my silver atom is neutral and oxygen has a coordination of 2 with silicon having a coordination of 4. After the deposition of ...
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2answers
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How is Persian blue rock salt made?

How is Persian blue rock salt made and what does it contain that makes it look blue?
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1answer
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Finding large databases of sphere packings

Part of my research is investigating sphere packings and their properties.I really would like a large database of sphere packings that I could investigate using a program I have written that tells me ...
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1answer
93 views

Are there any early industrial age methods capable of determining diamond or graphite's crystalline structure?

I'm writing a fictional story with early industrial age technology where a chemist discovers not only that diamond and graphite are made of the same substance, but that they differ by crystalline ...
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1answer
213 views

R32 Space Group

Which are the elements of the Twofold Screw Axis in this image? The "+" and "-" elements that intercept the red line are the elements of the Twofold Screw Axis 2/3? And if so, is the height of the ...
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1answer
227 views

Real space term for PPPM vs PME

I was under the impression that differences between the various long range electrostatic algorithms, ewald, PME, PPPM, to name a few, lied solely in their treatment of the reciprocal space term. ...
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1answer
2k views

Shapes of ionic compound

Can anyone explain the shapes of ionic compounds? What does it mean? What does the coordinate number mean? I know that in $\ce{NaCl}$, one $\ce{Na}$ atom is surrounded by 6 $\ce{Cl}$ atoms, and vice ...
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1answer
734 views

What determines the elastic limit of a substance?

from what I know, the elastic limit of a substance is the maximum amount of stress/force/pressure (a bit of confusion on my behalf here) a substance can withstand and still return to its original ...
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What factors contribute most to solubility of ionic substances in highly polar solvents, esp. ionic liquids and DES?

I am trying to determine a method to dissolve a mineral salt with a lattice energy of ≈18000 kJ/mol. I know that lattice energy is the most significant factor affecting solubility of an ionic ...
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Why are so many ionic compounds brittle?

Even when ionic compounds are strong (e.g. rubies and sapphires), they are neither malleable nor ductile in the slightest, and if sufficient stress is put on them, they will shatter, not bend. Why is ...
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What is the difference between an amorphous solid and glass?

They are both formed when a liquid is supercooled rapidly, no free energy, and they both have irregular structures. What defines a glass other than how it is amorphous, transparent, and has a glass ...